JP5321644B2 - Coating method - Google Patents

Description

  The present invention relates to a coating method for coating a coating liquid on the surface of a substrate to be conveyed.

  In recent years, electric vehicles such as hybrid vehicles and electric vehicles equipped with a motor as a drive source are becoming popular. Such an electric vehicle is equipped with a secondary battery for charging and discharging. The electrode of the secondary battery has a coating film formed by applying a coating liquid containing an active material, a conductive auxiliary material, a binder, etc. on the surface of a strip-shaped metal foil (base material) and drying it. Is used. In this secondary battery, when charging or discharging, ions are occluded or released between the positive electrode active material contained in the coating film of the positive electrode plate and the negative electrode active material contained in the coating film of the negative electrode plate. Done. In order to appropriately perform occlusion and release of ions, a coating film having an appropriate coating width (length in the substrate width direction) needs to be formed on the surface of the positive electrode plate or the negative electrode plate.

On the other hand, as a coating apparatus, an apparatus is known in which a coating liquid is discharged onto a surface of a substrate conveyed by a backup roll by a coating die located at a position facing the backup roll. The coating width of the coating film formed by the coating die changes according to the gap (coating gap) between the discharge port of the coating die and the substrate.
Therefore, for example, in Patent Document 1, the coating width of the coating liquid formed by the coating die is measured, and the coating gap is feedback-controlled based on the result of comparing the measured coating width with the target value. A coating method has been proposed. According to this coating method, the coating width can be feedback-controlled to the target value by adjusting the coating gap based on the measured value of the coating width.

JP 2007-258078 A

However, the above prior art has the following problems.
Generally, the coating liquid discharged by the coating die is pumped up from a supply tank by a pump or the like, and is supplied to the coating die through a supply circuit. Here, when the coating gap is changed, the pressure and flow rate of the coating liquid flowing through the supply circuit also change at the same time. When the pressure or flow rate of the coating liquid supplied to the coating die changes, the coating width also changes due to the influence.
Therefore, even if the coating gap is adjusted based on the measured value of the coating width as in Patent Document 1, the liquid pressure and flow rate of the coating liquid change by the change of the coating gap. Deviation occurs in the work width.
In this case as well, it is possible to feedback control the coating width to the target value by repeating the operation (feedback) to correct the coating width deviation by changing the coating gap again. There is a problem that it takes a relatively long time of about 3 to 5 minutes to stabilize.

On the other hand, since this type of coating line is generally operated continuously without holidays for 24 hours, after the production line is stopped, the operation of starting up again is performed several times a year. Therefore, in general, even if it took a little time to start up the coating line, there was no problem.
However, for example, if the coating line is stopped every day at night and is going to be run in the morning, or if it is operated continuously from Monday to Friday for 24 hours and stopped on Saturdays and Sundays, There is a strong demand for early stabilization of coating conditions (coating width, coating liquid pressure, flow rate, etc.) at the start. This is because when the production line is set up, the coating line is preliminarily operated until the coating conditions become stable. If the coating conditions are not stabilized early, the number of discarded products manufactured during the preparatory operation period increases. This is because the manufacturing cost increases. That is, in the conventional method, it takes about 3 to 5 minutes for the coating width to be stabilized by feedback control, and it is necessary to discard 100 m or more of the coated base material. It was a problem.

  The present invention has been made to solve the above problems, and provides a coating method capable of reducing discarded products in the preparation stage by stabilizing the coating width to a target value at an early stage. For the purpose.

In order to solve the above problems, the coating method of the present invention has the following characteristics.
(1) In a coating method for forming a coating film by discharging a coating liquid onto a surface of a substrate to be conveyed with a coating die, the coating liquid is applied between the coating die and a coating liquid supply tank. Detecting the pressure and flow rate of the coating liquid in the circulation circuit that circulates, estimating the viscosity of the coating liquid based on the detected pressure and flow rate, the estimated viscosity and the coating width of the coating die The initial value of the coating gap between the discharge port of the coating die and the base material necessary for setting the coating width as the target value is determined based on the correlation of Set to a value, start supplying the coating liquid to the coating die, and when changing the coating gap, the flow rate of the coating liquid is changed by feedforward control , To do.

(2) In the coating method described in (1), the coating width of the coating film coated by the coating die is measured, and the coating gap is feedback-controlled, and the coating gap When changing the flow rate, the flow rate of the coating liquid is changed by feedforward control.
(3) In the coating method described in (2), the change amount of the flow rate to be changed is determined based on the estimated viscosity and the change amount of the coating gap with respect to the initial value. To do.

The coating method having the above features has the following actions and effects.
(1) In a coating method for forming a coating film by discharging a coating liquid onto a surface of a substrate to be conveyed with a coating die, the coating liquid is applied between the coating die and a coating liquid supply tank. Detecting the pressure and flow rate of the coating liquid in the circulation circuit that circulates, estimating the viscosity of the coating liquid based on the detected pressure and flow rate, the estimated viscosity and the coating width of the coating die The initial value of the coating gap between the discharge port of the coating die and the base material necessary for setting the coating width as the target value is determined based on the correlation of Set to a value, start supplying the coating liquid to the coating die, and when changing the coating gap, the flow rate of the coating liquid is changed by feedforward control , Therefore, the change amount of the coating gap required after the supply of coating liquid to the coating die is started. Luo beforehand it becomes possible to reduce, it can be stabilized with a coating width to early target value.

That is, the present applicant has found through experiments that the coating width approximates a function of the coating gap (μm) and the viscosity of the coating solution (mPas). On the other hand, the viscosity of the coating liquid is known to vary depending on the lot difference of the coating liquid, the elapsed time after kneading the coating liquid, etc., but the viscosity of the coating liquid should be calculated theoretically. It is difficult. In particular, since the viscosity of the coating liquid stored in the tank is greatly different between the liquid in the upper layer and the liquid in the lower layer, it is more difficult to obtain the average value of the coating liquid in the entire tank. Met.
The applicant has confirmed that the viscosity of the coating liquid can be estimated fairly accurately based on these values by measuring the pressure and flow rate of the coating liquid flowing in the specified circulation circuit. did. In this case, it has been confirmed by experiments that the average viscosity of the coating liquid in the tank can be estimated by flowing a certain amount of the coating liquid through the circulation circuit.
Therefore, when starting up the coating line, circulate the coating liquid in the circulation circuit before starting coating, estimate the viscosity of the coating liquid, and determine the initial value of the coating gap from the estimated viscosity value. By setting up the coating line due to the coating gap, the coating width can be quickly stabilized at the destination, and the number of products to be discarded can be greatly reduced.

(2) In the coating method described in (1), the coating width of the coating film coated by the coating die is measured, and the coating gap is feedback-controlled, and the coating gap When changing the flow rate, the flow rate of the coating liquid is changed by feedforward control, so that the change in the flow rate of the coating liquid accompanying the change in the coating gap can be corrected quickly. The coating width can be stabilized to the target value at an early stage.

(3) The coating method described in (2) is characterized in that the change amount of the flow rate to be changed is determined from the estimated viscosity and the change amount with respect to the initial value of the coating gap. Since the change amount of the flow rate required for correction can be determined easily and quickly, the coating width can be stabilized to the target value at an early stage. In particular, since the pressure is greatly influenced by the viscosity, it is effective to perform this method when the viscosity is larger than a predetermined value.

It is sectional drawing which shows the whole structure of the coating control system which concerns on this embodiment. It is a graph which shows the relationship between the flow volume and pressure in a circulation circuit state, and a viscosity. It is a graph which shows the relationship between coating width and viscosity, and a gap. It is a control block diagram. It is a figure which shows the effect | action of coating width control. 5 is a graph showing the relationship between viscosity V / gap width G and flow rate F. It is explanatory drawing of coating width CL. FIG. 5 is a diagram illustrating a relationship between a coating width CL and a gap width G.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment embodying a coating control system according to the present invention will be described in detail with reference to the accompanying drawings. The coating control system of this embodiment controls the coating die 11 that coats the coating liquid 2 on the surface of the substrate 1 on which the electrodes are formed in the manufacturing process of the lithium ion secondary battery mounted on the electric vehicle. Is.
First, the overall configuration of the coating system according to the present embodiment will be described with reference to FIG. FIG. 1 is a conceptual diagram showing the overall configuration of a coating system according to this embodiment.

The coating die 11 ejects the coating liquid 2 from the fountain groove formed on the upper surface, forms a bead with the coating surface 1a of the substrate 1, and the coated bead of the substrate 1 is formed by the formed bead. It is an apparatus for applying the coating liquid 2 to the work surface 1a. On the upper surface of the coating die 11, there is a base material 1 that is held in close contact with the outer peripheral surface of the backup roll 13 with a gap having a gap width G. The backup roll 13 is rotated in the clockwise direction by the motor 14, and the base material 1 is conveyed in the direction indicated by the arrow A by another driving means.
As the base material 1 of this embodiment, metal foil, such as aluminum foil and copper foil, is used. As the coating material, a paste-like coating liquid 2 containing an active material, a conductive auxiliary material, a binder and the like is used.
FIG. 7 shows a perspective view of a part of the coating liquid 2 applied to the substrate 1. The coating width CL is the width of the coating liquid 2 coated on the substrate 1. Eventually, it is managed as the width of the coating material after being dried, but is managed as the width of the coating liquid 2 in the state after coating and before drying.
A follower roll 17 is provided on the upstream side of the backup roll 13 and holds the substrate 1. Further, a driven roll 15 is provided on the downstream side of the backup roll 13 and holds the substrate 1. A coating width measuring camera 16 is attached at a position facing the substrate 1 held by the driven roll 15. The coating width measuring camera 16 measures the width of the coating liquid 2 in real time and transmits measurement data to the central control device.

The coating die 11 is held so as to be movable in a direction close to or away from the axis of the backup roll 13. Further, a coating die moving motor 12 capable of accurately moving the coating die 11 in units of 1 μm is attached.
One end of a supply circuit 18 for supplying the coating liquid 2 is connected to the coating die 11. A supply circuit pressure sensor 25 is attached to an intermediate flow path of the supply circuit 18. The other end of the supply circuit 18 is connected to the second port of the switching valve 26 that is a three-way valve. A first port of the switching valve 26 is connected by a common circuit 20 to a discharge port of a monophone 23 driven by a servo motor. The monopump 23 can send an accurate amount of the coating liquid 2.
The input port of the monopump 23 is connected to a tank 24 that stores the coating liquid 2. A flow sensor 21 is attached to the common circuit 20. The third port of the switching valve 26 is directly connected to the tank 24 by the circulation circuit 19. A circulation circuit pressure sensor 22 is attached to the midway flow path of the circulation circuit 19.
The tank 24 stores a paste-like coating liquid 2 in which an active material, a conductive additive, a binder, a solvent, and the like are kneaded. The amount of the coating liquid 2 stored in the tank 24 is for several lots. One lot is an amount for coating the coating liquid 2 on the base material 1 of several thousand meters. The viscosity V of the coating liquid 2 may change by about 50% depending on the material and the elapsed time after kneading.

Next, the operation of the coating system having the above configuration will be described. For example, the case where the coating line is stopped on Friday night and the coating die 11 is washed will be described. At this time, as an example, it is assumed that the coating liquid 2 for one lot is still stored in the tank 24. When trying to restart the coating line on Monday morning, the viscosity of the coating liquid 2 may have increased by about 50%. When the coating line is started up as it is in the past, it takes about 3 to 5 minutes for the coating width CL to be stabilized by feedback control, and there is a risk that the coated substrate may be discarded more than 100 m. It was. Disposing of the base material every Monday morning has been a problem due to an increase in manufacturing costs.
In comparison, in the coating system of the present embodiment, first, the first port (common circuit 20) and the third port (circulation circuit 19) of the switching valve 26 are communicated, and the monopump 23 is operated. The coating liquid 2 is sucked up from the tank 24 and returned to the tank 24 through the common flow path 20, the switching valve 26, and the circulation circuit 19. This is the circulation circuit state. In the circulation circuit state, the flow rate sensor 21 measures the flow rate F in the circulation circuit state, and the circulation circuit pressure sensor 22 measures the pressure P in the circulation circuit state.

FIG. 2 is a graph showing the relationship between the flow rate / pressure and the viscosity in the circulation circuit state. The horizontal axis of the graph represents the flow rate of the coating liquid 2 (unit: g / min), and the vertical axis represents the viscosity (unit: Pas). P0 indicates a pressure curve when the pressure measured by the circulation circuit pressure sensor 22 is P0, P1 indicates a pressure curve when the pressure is P1, and P2 indicates a pressure curve when the pressure is P2. Yes. These data were obtained through experiments.
First, the pressure P in the circulation state is read from the circulation circuit pressure sensor 22, and the pressure curve P closest to the pressure value is selected. For example, when P1 is selected, the pressure curve P1 is selected. Here, when the measured pressure value is between P1 and P2, the intermediate value may be approximated by an approximation method.
Next, the flow rate F is read from the flow rate sensor 21. For example, it is assumed that the read flow rate is F1 (400 g / min as an example). As shown in FIG. 2, in the pressure curve P1, if the flow rate is F1, the viscosity V1 (for example, 400 mPas) is obtained. Thereby, the present viscosity V1 (400 mPas) of the coating liquid 2 stored for 3 days can be estimated.

FIG. 3 is a graph showing the relationship between the coating width CL / viscosity V and the gap width G. The horizontal axis of the graph is the coating width CL (unit is μm), and the vertical axis is the gap width G (unit is μm). The coating width CL is a difference with respect to the entire minimum reference width. In this embodiment, the gap width G has a maximum value of 100 to 200 μm, and can be controlled in units of 1 μm by the coating die moving motor 12. V0 indicates a viscosity curve when the estimated viscosity is V0, V1 indicates a viscosity curve when the estimated viscosity is V1, and V2 indicates a viscosity curve when the estimated viscosity is V2.
First, the viscosity curve closest to the viscosity estimated using FIG. 2 is selected. Next, the required coating width CL is determined. For example, it is assumed that the required coating width CL is CL1 (for example, the minimum reference width is 100 mm and the difference is 100 μm). The required coating width CL is a value given separately.
As shown in FIG. 3, in the viscosity curve V1 (400 mPas), if the coating width is CL1 (100 μm), GL1 (for example, 80 μm) is obtained as the gap width G.

Next, the coating die moving motor 12 is driven, and the gap width G between the outer surface of the substrate 1 held in close contact with the outer peripheral surface of the backup roll 13 and the upper surface of the coating die 11 is set to GL1. (80 μm).
Next, the switching valve 26 is switched to allow the first port (common circuit 20) and the second port (supply circuit 18) to communicate with each other. Further, the motor 14 is driven to rotate the backup roll 13 and the feeding of the substrate 1 is started.
As a result, the coating liquid 2 is applied to the surface of the substrate 1 through the supply circuit 18 and the coating die 11. The coating width CL is always measured by the coating width measuring camera 16.

  As described above, according to the coating method of the present embodiment, in the coating method of forming the coating film by discharging the coating liquid 2 by the coating die 11 onto the surface of the substrate 1 to be conveyed, Detecting the pressure P1 and flow rate F1 of the coating liquid 2 in the circulation circuits 19 and 20 for circulating the coating liquid 2 between the coating die 11 and the tank 24 of the coating liquid 2, and detecting the detected pressure P1 and Based on the estimation of the viscosity V1 of the coating liquid 2 based on the flow rate F1, and the correlation between the estimated viscosity V1 and the coating width CL of the coating die 11, the coating width CL1 is set as a target value. Determining the initial value GL1 of the coating gap G between the discharge port of the coating die 11 and the substrate 1, and setting the coating gap G to the initial value GL1 to the coating die 11. The supply of the coating liquid 2 to the coating die 11 is started. It is possible to advance small change amount of coating gap G required later can be stabilized with a coating width CL to early target value.

That is, the present applicant has found through experiments that the coating width CL approximates a function of the coating gap G and the viscosity V (mPas) of the coating liquid 2. Further, the coating liquid 2 is allowed to flow through the predetermined circulation circuits 19 and 20, the pressure P1 and the flow rate F1 at that time are measured, and the viscosity V1 of the coating liquid can be estimated fairly accurately based on those values. Was confirmed by experiments.
Therefore, when starting up the coating line, the coating liquid 2 is circulated in the circulation circuits 19 and 20 before the start of coating, the viscosity V1 of the coating liquid 2 is estimated, and the coating value 2 is estimated from the estimated value V1 of the viscosity V By determining the initial value GL1 of the working gap G and starting the coating line with the coating gap GL1, the coating width CL can be quickly stabilized at the destination, and the number of discarded products is greatly reduced. Can be made.

Next, management control of the coating width CL in operation will be described.
FIG. 4 shows a control block diagram. The gap width G is determined by the viscosity V and the coating width CL. Here, the viscosity V is determined by the flow rate F and the pressure P. The flow rate F is feedforward controlled (gain ΔF) by the gap width G and the viscosity V.
When the coating width CL of the coating liquid 2 is smaller than the reference value by a predetermined value or more, as shown in FIG. 8A, the coating die moving motor 12 is driven to narrow the gap width G. . As a result, the coating width CL widens and approaches the reference value. On the other hand, when the coating width CL is larger than the reference value by a predetermined value or more, as shown in FIG. 8B, the coating die moving motor 12 is driven to widen the gap width G. Thereby, the coating width CL becomes narrow and approaches the reference value.
On the other hand, when the gap width G is changed, the amount of the coating liquid 2 to be applied is changed, so that the pressure P measured by the supply circuit pressure sensor 25 and the flow rate F measured by the flow sensor 21 are changed. Change at the same time.
At this time, in this embodiment, for example, when the gap width G is widened to be the gap width GL2, the gap width G is changed to the gap width GL2 without waiting for feedback control of the coating width CL. At the same time, the command value to the monopump 23 is changed to change the flow rate F to the flow rate F2 that is a value adapted to the gap width GL2. That is, feedforward control is performed.

The operation is shown in FIG. Conventionally, since the change in the flow rate F is performed by feedback control, the flow rate greatly changes with Fa, and thus the fluctuation until convergence is large. However, in this embodiment, direct feedforward control is performed on the flow rate F2. Therefore, the flow rate can be converged to the flow rate F2 with a small fluctuation with the flow rate Fb.
Similarly, since the flow rate F2 converges with a small fluctuation, the pressure P can be converged with a small fluctuation Pb as compared with the fluctuation Pa by the feedback control.
According to the coating method of the present embodiment, the coating width CL of the coating film applied by the coating die 11 is measured by the coating width measuring camera 16, the coating gap G is feedback-controlled, and the coating is performed. Since the flow rate F of the coating liquid 2 is changed by feedforward control when the work gap G is changed, the change in the flow rate F of the coating liquid 2 due to the change of the coating gap G is promptly changed. Therefore, the coating width CL can be stabilized to the target value at an early stage.

On the other hand, in addition to the controls of FIGS. That is, the pressure P is greatly affected by the viscosity V of the coating liquid 2 as well as the gap width G. Therefore, when the viscosity V1 estimated by the circulation circuit 19 is larger than a predetermined value, it is good to correct by the following procedure.
FIG. 6 is a graph showing the relationship between the viscosity V / gap width G and the flow rate F. The horizontal axis is the gap width G (unit is μm), and the vertical axis is the flow rate F (unit is g / min). V0 is a viscosity curve when the viscosity is V0, V1 is a viscosity curve when the viscosity is V1, and V2 is a viscosity curve when the viscosity is V2.
In the viscosity curve, the viscosity increases in the order of V2, V1, and V0. When the estimated viscosity V is the viscosity V1, when the gap width G is changed from GL1 to GL1 ′, the gain ΔF in the feedforward control of the flow rate F performed in FIGS. A gain ΔF (change in flow rate when the estimated viscosity is the viscosity V1) may be used.
Accordingly, the amount of change in the flow rate F to be changed is determined from the estimated amount of change of the viscosity V1 and the initial value GL1 of the coating gap G. Since it can be determined easily and quickly, the coating width CL can be quickly stabilized to the target value.

It should be noted that the above-described embodiments and modifications thereof are merely examples and do not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention.
For example, in this embodiment, the circulation circuit pressure sensor 22 is provided in the circulation circuit 19 and the supply circuit pressure sensor 25 is provided in the supply circuit 18. However, the circulation circuit pressure sensor 22 is provided in the common circuit 20 to supply the pressure in the supply circuit. The sensor 25 may be omitted.
In this embodiment, the relationship between the flow rate / pressure and the viscosity in the circulation circuit state is stored in a graph, but it may be stored as an approximate expression and calculated. Similarly, the relationship between the coating width / viscosity and the gap may be stored as an approximate expression and calculated.
In this embodiment, the viscosity is once estimated, but the same can be said even if the gap is directly determined as a function of the flow rate, pressure, and coating width in the circulation circuit state. That is, even in such a calculation formula, it is considered that the viscosity is estimated from the flow rate and pressure.
In this embodiment, the coating width is measured by using the coating width measuring camera 16, but other optical sensors or sensors such as a film thickness sensor may be used.

DESCRIPTION OF SYMBOLS 1 Base material 1a Coating surface 2 Coating liquid 11 Coating die 12 Coating die moving motor 13 Backup roll 16 Coating width measuring camera 18 Supply circuit 19 Circulating circuit 20 Common circuit 21 Flow sensor 22 Circulating circuit pressure sensor 23 Mono pump 24 Tank 25 Supply circuit pressure sensor CL Coating width G Coating gap F Flow rate P Pressure V Viscosity

Claims (3)

In the coating method of forming a coating film by discharging a coating liquid with a coating die onto the surface of the substrate to be conveyed,
Detecting the pressure and flow rate of the coating liquid in a circulation circuit for circulating the coating liquid between the coating die and the supply tank of the coating liquid;
Estimating the viscosity of the coating liquid based on the detected pressure and flow rate;
Based on the correlation between the estimated viscosity and the coating width of the coating die, it is necessary to set the coating width as a target value, between the discharge port of the coating die and the substrate. Determining the initial value of the coating gap,
Setting the coating gap to the initial value and starting supplying the coating liquid to the coating die;
When changing the coating gap, changing the flow rate of the coating liquid by feedforward control,
A coating method characterized by In the coating method according to claim 1,
The coating width of the coating film applied by the coating die is measured, the coating gap is feedback controlled, and the flow rate of the coating liquid is fed when changing the coating gap. Changing by forward control,
A coating method characterized by In the coating method according to claim 2,
Determining a change amount of the flow rate to be changed based on the estimated viscosity and a change amount with respect to the initial value of the coating gap;
A coating method characterized by

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